The present invention relates generally to a measuring device, and more particularly to an apparatus and method for measuring elastomeric properties of a specimen during a test procedure.
Sealing members such as O-rings or gaskets are commonly made of elastomeric materials. Elastomeric materials are advantageous in that the O-ring made therewith is generally conformable, free of porosity, and relatively resilient thereby creating a relatively impermeable seal when positioned between two flat plates or flanges.
Over a period of time, the effectiveness of the seal created by an elastomeric O-ring may diminish. In particular, the O-ring is initially positioned between two plates or flanges, such as a mating flange of a water pump and a corresponding mating flange of a fluid inlet line, thereby compressing the O-ring when the two plates are secured to one another. The compressed O-ring exerts a force back against the two plates. Such a force is commonly and hereinafter referred to as a "sealing force" of the O-ring. Over a period of time, the sealing force of the O-ring relaxes or otherwise decreases thereby potentially causing a leak to occur between the two mating flanges in the case of the water pump and fluid inlet line.
A number of variables affect the rate at which the sealing force of the O-ring relaxes. For example, the type of elastomeric material which is used to make the O-ring affects the rate at which the sealing force of the O-ring relaxes. In addition, exposing the O-ring to an aging fluid such as air, water, gasoline, brake fluid, or engine coolant also affects the rate at which the sealing force of the O-ring relaxes. Moreover, exposing the O-ring to environmental conditions such as varying temperatures affects the rate at which the sealing force of the O-ring relaxes.
Therefore, a number of load measuring apparatuses have heretofore been developed to measure the rate at which the sealing forces of an elastomeric material relax. Such load measuring apparatuses, often referred to as relaxometers, generally include a test fixture in which an elastomeric test specimen is clamped. Such load measuring apparatuses further include a measuring instrument which is used to measure the sealing forces being exerted by the test specimen. The test fixture may be removed from the measuring instrument, and thereafter subjected to a variety of aging conditions such as heated fluid baths and ovens. After which, the test fixture is reinstalled in the measuring instrument in order to perform subsequent measurements.
There are a number of drawbacks associated with the use of the aforementioned load measuring apparatuses. For example, it is undesirable to repeatedly remove the test fixture from the measuring instrument. This is true since excessive handling of the test fixture may cause the test specimen to be jarred or otherwise moved, thereby potentially causing erroneous or otherwise invalid test data.
Moreover, the sealing force of the test specimen may only be measured at predetermined intervals during a test procedure. For example, the sealing force of the test specimen may be measured prior to placing the test fixture in an aging fluid bath. Thereafter, the test fixture may be removed from the aging fluid bath at predetermined intervals, such as every fifty hours, and placed in the measuring instrument in order to measure the sealing force at that particular interval. Hence, after 200 hours, relaxation of the sealing forces may be shown as the slope of a line with only five data points. Although the frequency of the intervals at which the test fixture is removed from the aging fluid bath may be increased, such frequency is for practical reasons limited by the amount of time necessary for an operator of the load measuring apparatus to (1) remove the test fixture from the aging fluid bath, (2) prepare the test fixture for measuring (e.g. clean the test fixture), (3) heat the test fixture to a testing temperature, (4) install the test fixture in the measurement instrument, (5) obtain the measurement, and (6) replace the test fixture in the aging fluid bath.
In addition, load measuring apparatuses which have heretofore been designed are relatively large thereby requiring a relatively large amount of space in a lab. Moreover, load measuring apparatuses which have heretofore been designed are relatively mechanically complex and financially expensive.
What is needed therefore is an apparatus and method for measuring elastomeric properties of a specimen during a test procedure which overcomes one or more of the above-mentioned drawbacks.